Safety switch



y 1942- H. T. SPARROW I 2,284,597

sAFETY. SWITCH Filed July 31, 1940 ATTOR N EY Patented May 26, 1942 ,UNlTED STATES PATENT OFFICE.

SAFETY SWETCH Hubert T. Sparrow, Minneapolis, Milllh, assignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Application July 31, 1940, Serial No. 348,705

11 Claims.

The present invention is concerned with a safety switch and more particularly with one which normally occupies one predetermined circuit controlling position except upon the occur-.

rence of an abnormal condition.

There are many cases'in which it is desirable to employ a switch which is either normally closed or open and is moved to another circuit,

controlling position upon the occurrence of an abnormal condition. One typical application of such a switch is in the gas burning art wherein it is desirable to insure that gas will not flow to the main burner unless the pilot burner is burning. It has been proposed to use for this purpose an electromagnetic switch, the electromagnet of which is energized by a thermocouple. The hot junction of the thermocouple is exposed to the flame of the pilot burner so that the thermocouple maintains the electromagnet energized as long as the pilot burner is ignited.

The electromagnet is designed to hold a switch or some other controlling device in what may be ent wherein the various advantageous features are obtained with a much more simple and insafety feature. above discussed is obtained by means of an extremely simple construction.

Other objects of the invention will be apparent from a consideration of the accompanying speoiflcation, claims and drawing of which Figure 1 is a vertical sectional view of the improved switch, the section being taken along termed an active position so long as the electromagnet is energized. Thus where the controlling device is a switch, this switch may be in series with an electrically operated gas valve, the switch being normally closed as long as the electromagnet is energized. Upon extinguishment of the pilot burner, the electromagnet becomes deenergized and the switch is moved to open position to prevent the energization of the gas valve or to, cause its deenergization if already energized. Such an electromagnetic switch is disclosed in the patent to Carl G. Kronmiller No. 2,165,801 issued July ll, 1939.

In such a device it is often desirable that the thermocouple be incapable of energizing the electromagnet sufficiently to reclose the switch so that it is necessary to manually reengage the armature and electromagnet. In effecting such reengagement it is highly desirable that the switch not be moved to a position permiiting energization of the gas valve until the electromagnet has actually become energized sufficiently to hold the armature. If the switch is not so designed, it is possible to admit gas to the main burner before the pilot burner is ignited each I time that it is atempted to reset the device.

The construction in the above mentioned Kronmiller patent provides an arrangement wherein it is impossible to reclose the switch unil the electromagnet has actually held the armature.

It is broadly an object of the presen invention to provide an improved construc'ion of the type shown in the above mentioned Kronmiller patthe line i--l of Figure 2,

Figure 2 is an elevational end view of the construction, the view being taken from the right of Figure 1,

Figure 3 is a transverse sectional view, the section being taken along the line 3--3 of Figure 1 and being taken wiih the switch in its normal active position,

Figure 4 is a view similar to Figure 3 but showing the switch elements in the position assumed when the electromagnet is deenergized, and

Figure 5 is a fuel burner control system embodying the improved switch.

Referring specifically to the drawing, it will i be noted that the improved device is housed in a switch casing I0 and an electromagnetic hous-.

. is a material commercially known as Allegheny metal, an alloy containing approximately 49.2% nickel, 50% iron, 0.6% manganese and 0.2% silicon. Welded or otherwise rigidly secured to the cup shaped portion I5 is a flanged extension sleeve IE which may be formed of any other material preferably non-magnetic. The flange of the sleeve 56 and the flange :3 are held together with oircumferentially spaced screws l1.

' member 26 and the housing portion l5. It will be noted that this armature is substantially the same diameter as the portion l5 and simultaneously engages the annular edge of this portion and the end of core 26. Surrounding the core portion 26 is an electromagnetic winding 22 which is preferably formed of a flat strip of copper or other material of high electrical conductivity. The copper strip is wound spirally with a layer of insulating material which serves to separate the turns of the copper strip adjacent each other. Surrounding the coil 22 is a compression spring 23 which bears against the armature .2| and biases it away from the core.

Extending through the left hand end of the housing II are terminal posts 24 and 25. These terminal posts take the form of threaded bolts the heads of which are of non-circular cross section. It will be noted that there are two insulated discs 26 and 21 within the left hand end of the housing II. The extreme left of these discs is provided merely with two apertures of a size just sufficient to permit the bolts 24 and 25 electromagnet compartment within hous- 41 and 46 are normally in engagement. The switch blade 34 is relatively rigid and due to the bias of switch blade 35,'contacts 45 and 46 are normally separated. Upon switch blade 35 being moved upwardly, as viewed in Figure 3, contacts 45 and 46 are moved into engagement. The positioning of the switch blades "is controlled by two opposed members 56 and 5|. Member56 is positioned by the armature 2| and member 5| is manuallypositioned by means of a push button extension 12 projecting through the right hand wall of housing l6. The two members 56 and 5| are axially aligned and are both reciprocable.

The two members have opposed conical faces 52 vided with inclined wings 56 and 51 to cooperate with theinclined-faces52 and 53 of members to extend therethrough. The disc 21 is however provided with two non-circular apertures of the same configuration as the heads of bolts 24 and 25 so that the bolt heads are retained non-rotatably therein. Threaded washers 28 and 29 are secured over the terminal bolts 24 and 25 to hold these terminal members in position and to provide a clamping surface for the conductors to be connected to the terminals. An insulating V washer 36 is shown as interposed between the washer 29 and the outer wall of housing II. If

' desired, a similar washer can be, incorporated between the washer 28 and the housing |l ,although in many cases it is found desirable to have one terminal electrically connected to the housing. The usual terminal nuts 3| and 32 are threaded on the terminal posts 24 and 25.

Referring to the switch housing, it will be noted that there are three switch blades 34, 35, and 36. Each one of these is secured to a ter- .minal member, the respective terminal members being designated by the reference numerals 31, 38, and 36. Each one of these terminals is provided with a slot through which the end of the switch blade extends and in which it is immovably held by soldering, swaging, or some similar operation. As indicated in connection with terminal 31 in Figure 1, each terminal is provided with a cylindrical extension 4| which extends through an aperture in the right hand wall of casing l6. The extension 4| further extends through an opening and terminal washer 42, the outer end of the extension 4| being swaged to hold the terminal member 31 rigidly in position. The extension 4| has a tapped hole to receive a terminal screw 43. r

The switch blade 34 carries a contact 45, the switch blade 35 contacts 46 and 41, and the switch blade 36 a contact 48. The switch blades 35 and 36 are biased together so that contacts thermocouple as the energizing means.

56 and 5|. The member 56 is secured to armature 2| by means of a U-shaped bracket 58 which.

provided with a collar 6| which rests against the inner wall of a cylindrical recess'62 in member 56, the bolt being provided with an elongated stem 63. Member 5| is also provided with a cylindrical recess corresponding to recess 62. A spring 66 has its ends located in the recesses 62 and 65 and.serves to bias members 56 and 5| apart. The stem 63 serves the dual function of limiting the movement of members 56 and 5| toward each other and also serves as a guide for spring 66. The spring 66 is considerably lighter than spring 23 so that when the latter spring is not otherwise restrained it is able to compress spring 66.

The electromagnet Winding 22 is normally energized by connection of the terminals 24 and 25 with some energizing source. This may be a commercial source of electricity with condition responsive switches controlling the connection of winding 22 to the source. The present switch is particularly designed, however, to employ a Whatever the source of energization is, it is selected so as to be sufficient to enable the electromagnet to hold the armature in engagement therewith against the action of biasing spring 23 but insuflicient to cause such engagement after the armature has once separated fromthe electromagnet.

During the period that the electromagnet is energized members 56 and 5| are in the position shownin Figure l, the member 56 being so held by the attractionof armature 2| by the electromagnet. The spring 66 serves to bias member 5| to the position shown in Figure 1. In the position occupied by members 56 and 5| in Figure 1, neither of these members is in engagement with the switch blades 35 and 36 so that these blades are allowed to move together by reason of their bias to assume the position shown in Figure 3. In this position, contacts 41 and 48 are in engagement. As soon as the electromagnet is deenergized for any reason however, the spring 23 is effective to move armature 2| to the right. This movement of armature 2| causes member 56 similarly to move to the right so that the conicalsurface 52 enters between and spreads the switch blades 35 and 36 apart. The movement of switch blade 35 as a result of this spreading action results in contact 46 carried thereby being moved into engagement with contact'45. This action is illustrated in Figure 4. The movement of member 56 is guided by'the wings 56 and inwardly to the left. This is facilitated by the provision of the push button extension 12. Upon member being moved to the left, the conical surface 53 enters between switch blades 35 and '15 to insure that contacts 41 and as will be held out of engagement and contacts 45 and 48 will be held in engagement. Upon the member 5| being moved still further to the left, the innermost wall of the recess 85 will engage the end of stem 83 so that upon further inward movement of -member 5|, member 58 will be moved to the left. This movement of member 58 will cause simultaneous movement of armature 2| against the action of spring 23 until armature 2| is moved into engagement with the core formed by members l5 and 28. If the electromagnet is now energized, it will be effective to retain armature 2| and member 58 in the position shown in Figure 1 so that upon release of button 12, the spring 86 will move member 5| to the position shown in Figure 1, permitting the switch blades 35 and 38 to move together to effect engagement of contacts 41 and 48. If, however, the electromagnet is not energized, the member 58 will travel back with member 5| as the latter member is released so that before -member 5| is moved to aposition which would otherwise permit engagement of contacts 41 and 48, the member 58 has entered between the blades '35 and 38 to maintain contacts 41 and 48 separated. Thus as long as the elcctromagnet is deenergized it is impossible even momentarily to cause engagement of contacts'41 and 48.

From the foregoing description, .it should be apparent that the members 50 and 5| may be termed control members, in that they control the opening and closing of the circuit through the switch blades 35 and 36. Furthermore, since the circuit in question is closed when the parts are in the positions shown in Figures 1 and 3, that position of the control members 58 and 5| may be termedtheir active position. On the other hand, the position of the .control members 58 and 5| shown in Figure 4, in which position the circuit through blades 35 and 38 is open, may be termed the safe position of members 58 and 5|. I

In Figure 5, I have shown a fuel burner control system employing my improved switching mechanism. Referring to this figure, a main gas burner is designated by the reference numeral 15-. This burner is supplied with gas by a main gas supply pipe 18' in which is interposed an electrically operated motorized valve 11. This ing II. This thermocouple 80 has its hot junction in the flame issuing from pilot burner 18 and is normally effective to energize the electromagnet 22 sufilciently to maintain switch ,blades 35 and 38 in contact making position,

as shown in Figure 5.

A thermostat 84 controls the energization of the motorized valve 11. This thermostat comprises a bimetallic element 85 and a contact arm 88 secured thereto. The contact arm .88 is adapted to be moved into engagement with a fixed contact 81 upon the temperature falling to a predetermined value. The thermostat 84 is responsive to the temperature of the space being heated by burner 15 or of some other suitable controlling medium.

A signalling device 89 is provided to indicate when the pilot is extinguished. This signalling device is shown specifically as a lamp located near the thermostat 84.

A step down transformer 9| is employed for controlling the energization of the valve 11 and the signalling device 89. This transformer comprises a line voltage primary 92 and a low voltage secondary 93, the primary being connected to any suitable source of power not shown.

Whenever thethermostatic switch blade 88 is engaged with contact 81, a circuit is established to valve 11 as follows: from the lower terminal of secondary 93 through conductor 95, switch blade 35, contacts 41 and 48, switch blade 38, conductor 96, motorized valve 11, conductor 91, bimetallic element .85, contact arm 88, contact 81, and conductors 98 and 99 to the other terminal of secondary 93. The motorized valve isthus energized to admit gas to the main burner. It will be noted that this circuit depends upon the closure of contacts 41 and 43, these contacts being closed so, long as the pilot burner 18 is ignited. Whenever the pilot burner becomes extinguished, the hot junction of the thermocouple rapidly assumes the 'same temperature as the cold junction to cause deenergization of the electromagnet 22. This causes contacts 41 and 48 to be separated and contacts 45 and 46, to be made, as previously described. The separation of contacts 41 and 48 results in the'deenergization of motorized valve 11. The engagement of contacts '45 and 48 causes the energization of signal lamp 89 as follows: from the lower terminal of secondary 93 through con.. ductor 95, switch blade 35, contacts 48 and 45, conductor IIH, switch blade 34, signal lamp 89, and conductors I82 and 99 to the other terminal secondary 93. Thus shortly after the pilot is extinguished, the valve is deenergized so as to move to closed position andthe signal lamp 89 is energized to warn theuser of the heating valve is of the type which remains open so long as it is energized but is closed immediately upon deenergization thereof. A pilot burner is designated by the reference numeral 18. This pilot burner is connected by means of a pipe 19 to the supply pipe 18 on the supply side of valve 11. Thus pilot burner 18 is normally-constantly burning.

The switching mechanism of the present invention is shown in schematic form, the same reference numerals being applied to the switch blades and contacts as in the preceding figures. A thermocouple 88 is shown as connected by conductors 8| and 82 to the terminals of housequipment that the pilot has become extinguished.

The signal light 89 will remain energized until the electromagnet 23 has become reenergized and the armature moved into reengagement therewith. It is impossible to deenergize signal lamp 89 and permit the opening of valve 11 by tieing or otherwise mechamcally holding button 12 in. The only way inwhich the signal lamp can be deenergized and the valve 11 reenergized is by the retention of armature 2| by the electromagnet following the release of buttons 12.

While I have shown the specific embodiment of the invention for purposes of illustration, it is to be understood that the invention is limited only by the scope of the appended claims.

I claim as my invention: 1. In combination, a pair of switch elements biased into a first circuit controlling position and so that portions thereof tend to move together, a pair of members each adapted to enter v between said portions of said elements and move them apart to move said switch elements to a second circuit controlling position, means for continuously biasing a first of said members to a position between said elements, and releasable holding means for retaining'said first member in a position spaced from said elements, said holding means comprising an electromagnet and an armature one of which is fixedly mounted and the otherof which is connected to said first member, said other member being so disposed with respect to said first member that movement of said other member in one direction is effective to cause it to enter between said portions of said switch elements and simultaneously to move said first member so asto move said electromagne't and armature together.

2. In combination, a pair of switch elements biased into a first circuit controlling position and so that portions thereof tendto movetogether, a pair of members each adapted to enter between said portions of said elements and move them apart to, move said switch elements to a second circuit controlling position, means for continuously biasing a first of said members to a position between said elements, and releasable holding means for retaining said first member in a position spaced from said elements, said holding means comprising a fixedly mounted electromagnet and an armature connected to said first member, said second member being so disposed with respect to said first member that movement of said second member in one direction is effective to cause it to enter between said portions of said switch elements and simultaneously to move said first member and armature to a position in which said armature engages said electromag'net.

3. In ccmbinatio'rna pair of switch elements biased into a first circuit controlling position and so that portions thereof tend to move together, a pair of aligned reciprocable members normally disposed on opposite sides of said switch eleswitch elements in said second circuit control-- ling position, releasable holding means normally effective to retain said first member in a position spaced from said elements, and means biasing said second member to another position spaced from said elements, said second member being effective when moved toward said first member to enter between said portions of said beveled portions in alignment with said mem bers for engaging said faces, and holding means for retaining a first of said members in a position spaced from said elements, said holding means comprising an electromagnet and an armature one of which is fixedly mounted and the other of which is connected to said first member, said other member being, operable upon movement thereof in the direction of said switch blades to hold said switch blades apart and to move said first member so as to move said electromagnet and armature together.

5. In combination, a pair of elongated resilient, switch blades having portions spaced from and substantially parallel to each other, said blades also having portions offset toward each other at one end and having relatively hard contact members supported on said offset portions, one of said contact members extending through its associated blade, said blades being separately supported at their other ends so as to bias said contacts into engagement, a third contact resiliently supported adjacent said one contact member and spaced therefrom when said first mentioned contact members are in engagement, a pair of aligned reciprocable operating members normally disposed on opposite sides of said parallel portions and movable. transversely thereto, said members being wider than the space between said parallel portions, said blades and said members having mating surfaces thereon so that movement of either of said members between said blades causes engagement of said surfaces,

, separation :of said first-mentioned contacts and engagement of said third contact with said one contact, means continuously biasing one of said operating members for movement to a position between said blades, releasable holding means for retaining said one operating member in a position wherein it is disengaged from said blades, the other of said operating members being effective when moved between said blades to engage said one operating member and move it to said disengaged position.

6. In combination, control means comprising a substantially cylindrical member movable between a first safe position and a second active position, a casing for said control means, means within said casing for engaging the sides of said. cylindrical member when said member is inits safe position, said last-mentioned means having an aperture therein through which at least a portion of said cylindrical member passes when switch elements and simultaneously to move said first member to the position where said holding means is normally effective to retain it.

4. In combination, a pair of switch blades biased together into contact making engagement, a pair of aligned recipr'ocable substantially cylindrical members normally disposed on opposite sides of said switch blades and having opposed substantially conical faces, each of said members being adapted .to move transversely to said blades and insert said faces between said blades and force them apart, said blades having in said safe position, a cup shaped housing secured to said casing, an electromagnet including a core supported centrally of said housing, an armature within said housing adapted to be moved into engagement with said core, a flexible diaphragm clamped between said housing and said control means casing and forming a partition wall therebetween, means extending through said diaphragm for clamping said armature, said diaphragm, and said member together, a reciprocable member for manually moving said cylindrical member, said reciprocable member being mounted through the bottom of said cas ing coaxially with said cylindrical member, and a lost motion connection between said members comprising a coil spring engaging to both said members and a pin attached to one of said members and extending centrally of said coil spring, said diaphragm and clamping means cooperating with said coil spring and pin to support said cylindrical member centrally of said casing and to guide said member in its movement between said first'and second positions.

'7. In combination, control means comprising a substantially cylindrical member movable be;- tween a first safe position and a second active position, a casing for said control means, means within said casing for engaging the sides of said cylindrical member when said member is in its safe position, said last-mentioned means having an aperture therein through which at least a portion or said cylindrical member passes when in said sate position, a cup shaped housing secured to said casin an electromagnet including a core supported centrally or said housing, an armature within said housing adapted to be moved into engagement with said core, a flexible diaphragm clamped between said housing and said control means casing and forming a partition wall therebetween, means for clamping said armature, said diaphragm, and said member together including a pin having a threaded portion extending through said member and said diaphragm and an elongated shank portion extending beyond said member, a reciprocable member for manually moving said cylindrical member, said reciprocable member being mounted through the bottom or said casing coaxially with said cylindrical member, both said members having substantiailly cylindrical opposed recesses therein, the recess in said cylindrical member surrounding the elongated shank portion ofsaid pin, and a lost motion connection between said members comprising said shank portion 01 said pin and a coil spring surrounding said pin having its ends received in said recesses, said'diaphragm, pin and spring cooperating to support said cylindrical member centrally of said casing and to guide said member in its movement between said first and second positions.

8. A control device, comprising in combination, a first control member movable between a first safe position and a second active position, a casing for said control device, control means within said casing for cooperatively engaging said movable member when said member is in its safe position, said control means having an aperture therethrough, a housing secured to said casing, an electromagnet including a core supported within said housing, an armature within.

said housing adapted to move into engagement with said core, a partition between said housing and said casing including a flexible diaphragm, means extending through said diaphragm i'or clamping said armature, said diaphragm, and said member together, a second control member for manually moving said first member, said second member being mounted through a portion 01" said casing in alignment with said first member, and a lost motion connection Joining said members and extending through said aperture, said lost motion connection comprising a coil spring engaging to both said members and a pin attached to one 01' said members and extending centrally or said coil spring, said diaphragm and clamping means cooperating with said coil spring and pin to support and to guide said first member in its movement between said first and second positions.

9. A control device, comprising in combination, a first control member movable between a first safe position and a second active position, a casing for said control device, control means said movable member when said member is in its safe position, a housing secured to said casing, an electromagnet including a core supported within said housing, an armature within said housing adapted to move into engagement with said core, a partition between said housing and said casing including a flexible diaphragm, means extending through said diaphragm for clamping said armature, said diaphragm, and said member together, a second control member for manually moving said first member, said second member being mounted through a portion of said casing in alignment with said first member, and a lost motion connection Joining said members and comprising a coil spring engaging to both said members and a pin attached to one of said members and extending centrally of said coil spring, said diaphragm and clamping means cooperating with said coil spring and pin to support and to guide said first member in its movement between said first and second positions.

10. In combination, a switch element biased to a first circuit controlling position and movable to a second circuit controlling position, a pair of aligned reciprocable members normally disposed on opposite sides of said element and having opposed faces, each of said members being adapted to move in the direction of said element, thereby engagingsaid element with one of said faces and moving it laterally to said second position, means continuously biasing a'first of said members into engagement with said element to hold said element in said second position, releasable holding means normally effective to retain said first member in a position spaced from said element, and means biasing said second member to another position spaced from said. element, said second member being effective when moved toward said first member to engage said element and hold it in its second position and simultaneously to move said first member to the position where said holding means is normally effective to retain it.

11. A control device, comprising in combination, a first control member movable between a first sate position and a second active position, a casing for said control device, control means within said casing for cooperatively engaging said movable member when said member is in its safe position, a housing secured to said casing, an

said housing, an armature within said housing adapted to move into engagement with said core, a flexible element supported at its sides on said casing, means extending through said element substantially centrally thereof for clamping said armature, said element and said member together, a second control member for manually moving said first member, saidsecond member being mounted through a portion of said casing in alignment with said first member, and a lost motion connection Joining said members and comprising a coil spring enga ing to both said members and a pin attached to one of said members and extending centrally of said coil spring, said element and clamping-means cooperating with said coil spring and pin to support and to uide said first member in its movement between said first and second positions.

' HUBER! '1'. SPARROW. 

